The present invention generally relates to an aircraft environmental control system (ECS). More specifically, the present invention relates to an ECS where the fresh air for the cabin is provided by electric motor driven compressors in place of traditional engine bleed air.
Modern jet airplanes operate in a physical environment that is not survivable by unprotected humans. Thus, these airplanes contain a complex ECS to enable survival, safety and comfort for the aircraft passengers.
Referring to FIG. 1, there is shown a bleed system of a conventional aircraft with a Pratt and Whitney (PandW) 4000 engine. As outside air enters the compressor stages 100 of the engine, it is compressed to about 32 psi and a temperature of about 330xc2x0 F. Some of this air is then extracted from the engine core through either a high pressure bleed port 110 or a low pressure bleed port 120, depending upon the pressure requirements at any given time. A shut-off valve 130 adjusts the feed from high pressure bleed port 110 depending on aircraft systems requirements.
The bleed air passes through a precooler 140 to help regulate the temperature and pressure of the bleed air delivered to meet the pneumatic services of the airplane, such as water pressurization, wing and engine anti-ice protection, hydraulic pumps, trim air for cabin warming, and the like.
The precooled air for the conventional ECS travels through air conditioning packs (not shown) to provide essentially dry, sterile, and dust free conditioned air to the airplane cabin. This conditioned air is then mixed with a predetermined amount of cabin recirculated air and delivered to the aircraft cabin. Trim air, taken downstream of precooler 140, may be added to warm the conditioned air to a suitably comfortable level for the aircraft cabin.
At the beginning of the commercial jet airliner age, jet airplanes did not have cabin air recirculation systems. The primary reason was that early jets were powered by highly inefficient turbojet engines. In the turbojet, all of the air entering the engine went through the core. Thrust was obtained by extremely high velocity, high energy turbine exhaust. Fuel consumption was very high, but the additional fuel required to provide outside air to the cabin was very small because the bleed air extraction was a small percentage of the total core airflow.
As engine technology progressed, turbofans were developed with a core bypass ratio of approximately 2 to 1. That is, only about one-half of the air drawn into the engine enters the core. The bulk of the air goes through the bypass portion of the engine to produce most of the engine thrust. Fuel economy improved and the cost of engine bleed air relative to overall fuel consumption was still sufficiently small to make 100% bleed air to the passenger cabin cost effective. The economics at that time were also affected by shorter average flight lengths and a lower percentage of direct operating costs attributed to fuel than today.
As modern turbofan engines with high 5 to 1 bypass ratios were developed, fuel consumption to provide engine thrust decreased. However, the fuel consumption relative to extracting bleed air dramatically increased, almost in direct proportion to the higher bypass ratio. For a 767 aircraft with PandW 4000 engines, the percent increase in fuel consumption due to bleed air only would be almost four times higher than an equivalently sized turbojet. With rising fuel costs and the development of more efficient engines, this relative increase in fuel consumption for bleed air becomes quite significant.
As can be seen, there is a need for an improved ECS which overcomes the disadvantages of the conventional ECS systems as discussed above.
In one aspect of the present invention, an environmental control system for providing conditioned air to a substantially enclosed space, comprises at least one air compressor for pressurizing fresh air from outside the space to provide pressurized fresh air; at least one vapor cycle pack for conditioning the pressurized fresh air from the at least one air compressor to provide conditioned air; and an air distribution system for delivering the conditioned air to the space.
In another aspect of the present invention, an environmental control system for providing conditioned air to a substantially enclosed space comprises at least one air compressor for pressurizing fresh air from outside the space to provide pressurized fresh air; the at least one electric air compressor providing heat to warm the fresh air without the requirement of a resistance heating element; at least one vapor cycle pack for conditioning the pressurized fresh air from the at least one air compressor to provide conditioned air; an air distribution system for delivering the conditioned air to the space; a recirculation add heat valve to recirculate air from an output of the compressor back into an input of the compressor; an air fan for recirculating air from the space into the pressurized fresh air prior to passing through the at least one vapor cycle pack; and a precooler for cooling the pressurized fresh air prior to entry into the at least one vapor cycle pack.
In a further aspect of the present invention, an environmental control system for an aircraft to provide a flow of conditioned air within at least a cabin portion of the aircraft comprises at least one cabin air compressor for pressurizing fresh air from outside of the aircraft to provide pressurized fresh air; at least one vapor cycle packs for conditioning the pressurized fresh air from the plurality of cabin air compressors to provide conditioned air; and an air distribution system for delivering the conditioned air to a cabin of the aircraft.
In yet a further aspect of the present invention, an environmental control system for an aircraft to provide a flow of conditioned air within at least a cabin portion of the aircraft comprises at least one cabin air compressor for pressurizing fresh air from outside of the aircraft to provide pressurized fresh air; at least one vapor cycle pack for conditioning the pressurized fresh air from the at least one cabin air compressor to provide conditioned air; an air distribution system for delivering the conditioned air to a cabin of the aircraft; a recirculation add heat valve to recirculate air from an output of the cabin air compressor back into an input of the cabin air compressor; a cabin air fan for recirculating air from the cabin into the pressurized fresh air prior to passing through the at least one vapor cycle pack; and a precooler for cooling the pressurized fresh air prior to entry into the at least one vapor cycle pack.
In a still further aspect of the present invention, a method for supplying conditioned air to at least a cabin area of an aircraft comprises pressurizing fresh air from outside the aircraft with at least one cabin air compressor to provide pressurized fresh air; conditioning the pressurized fresh air with at least one vapor cycle pack to provide conditioned air; and distributing the conditioned air to the cabin area of the aircraft.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.